1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member having a photosensitive layer containing a specific compound as a charge-generating material. This invention also relates to a process cartridge and an electrophotographic apparatus which have such electrophotographic photosensitive member.
2. Related Background Art
Phthalocyanine pigments are not only used for coloring, but also have long attracted notice and have been studied as electronic materials used in electrophotographic photosensitive members, solar cells, sensors and so forth.
In recent years, printers to which electrophotography is applied are also in wide use as terminal unit printers. These are chiefly laser beam printers having lasers as light sources. As the light sources, semiconductor lasers are used in view of the cost, the size of apparatus and so forth. Semiconductor lasers prevailingly used at present have an oscillation wavelength of as long as 790 to 820 nm. Accordingly, electrophotographic photosensitive members having sufficient sensitivities in such a long-wavelength region are being developed.
Sensitivity regions of electrophotographic photosensitive members differ depending on the types of charge-generating materials. In recent years, as charge-generating materials having a sensitivity to long-wavelength light, substantial research has been conducted on metal phthalocyanines or metal-free phthalocyanines such as aluminum chlorophthalocyanine, chloroindium phthalocyanine, oxyvanadium phthalocyanine, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, magnesium phthalocyanine and oxytitanium phthalocyanine.
Of these phthalocyanines, oxytitanium phthalocyanine is disclosed in Japanese Patent Application Laid-open Nos. 61-217050, 61-239248, 64-17066 and 3-128973. Hydroxygallium phthalocyanine is disclosed in Japanese Patent Application Laid-open Nos. 5-263007 and 6-93203.
As a combination of charge-generating materials, Japanese Patent Application Laid-open Nos. 3-37666, 5-66596 and 7-128888 disclose an electrophotographic photosensitive member having a broad sensitivity wavelength region (i.e., panchromatic), using a phthalocyanine compound and an azo pigment in combination.
An electrophotographic photosensitive member making use of an oxytitanium phthalocyanine having the strongest peak at 27.2.degree..+-.0.2.degree. of the diffraction angle (2.theta.) in CuK.alpha. characteristic X-ray diffraction has a very high sensitivity and also a good charging performance, but those having much superior characteristics with respect to residual potential, photomemory and potential stability are under study. Also, an electrophotographic photosensitive member making use of a hydroxygallium phthalocyanine having strong peaks at 7.4.degree..+-.0.2.degree. and 28.2.degree..+-.0.2.degree. of the diffraction angle (2.theta.) in CuK.alpha. characteristic X-ray diffraction shows good results for sensitivity, residual potential and photomemory, but those having much superior characteristics with respect to charging performance and potential stability are being sought.
In order to improve characteristics, e.g., to broaden the sensitivity region, it is proposed to use a phthalocyanine compound and a azo pigment in combination. However, a difference in dispersibility between the phthalocyanine compound and the azo pigment requires a complicated dispersion method or results in an unstable dispersion in many cases. Also, from the viewpoint of achieving much higher process speed and much higher image quality, studies are being made on electrophotographic photosensitive members having much superior characteristics with respect to sensitivity, potential stability in repeated use, residual potential, black dots or fog due to faulty charging, and also memory to white light.